<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    
</body>
<script>
    // 输入框
    let r = parseFloat(prompt('请输入圆的半径：'));
    // 周长
    let circle = Math.PI * 2 * r;
    // 面积
    let area = Math.PI * Math.pow(r, 2);
    // 打印，四舍五入两位小数
    console.log(`圆的半径是${r}，周长为${circle.toFixed(2)}，面积为${area.toFixed(2)}`);
</script>
</html>